Pin Charmed Operator Framework version for charms

Change-Id: Iff5659151e5678298b72e54b7b22a375bc7b7ebf
Signed-off-by: Dario Faccin <dario.faccin@canonical.com>
(cherry picked from commit d0303f5fff9c744aa101767166e94277c9e3259f)
diff --git a/installers/charm/osm-nbi/tox.ini b/installers/charm/osm-nbi/tox.ini
index e24bef5..23ecc4c 100644
--- a/installers/charm/osm-nbi/tox.ini
+++ b/installers/charm/osm-nbi/tox.ini
@@ -63,7 +63,7 @@
 commands =
     # uncomment the following line if this charm owns a lib
     codespell {[vars]lib_path}
-    codespell {toxinidir}/. --skip {toxinidir}/.git --skip {toxinidir}/.tox \
+    codespell {toxinidir} --skip {toxinidir}/.git --skip {toxinidir}/.tox \
       --skip {toxinidir}/build --skip {toxinidir}/lib --skip {toxinidir}/venv \
       --skip {toxinidir}/.mypy_cache --skip {toxinidir}/icon.svg
     # pflake8 wrapper supports config from pyproject.toml